1. Field of the Invention
This invention relates generally to apparatus for removing articles from molds, and more particularly to removing undercut articles from their corresponding undercut molds.
2. Discussion of the Prior Art
Many articles of rubber, plastic, and other materials are mold-formed by pressure differential, such as vacuum molding. Vacuum molding is a means of pulling sheet material tightly against a mold form by the introduction of a vacuum form within the mold form.
Apparatus and methods for removing articles from their molds have wide application. Many apparatus and methods have been devised for removing the articles, once formed, from their corresponding molds. The various apparatus and methods have required varying types of molds, e.g., flexible, inflexible, movable, and separable molds. The types of molds used depends upon the type or shape of the article being formed. When the article was formed in portions and later sealed together, the type of mold, as to whether it was flexible, separable, etc., depended on factors other than the shape of the article itself. However, in forming undercut articles, the article of necessity is formed in sections and later sealed together, or the mold itself is in sections to split away from the article after it is formed.
When a whole undercut article is formed about a one-piece male mold mandrel, it was necessary that the mandrel be flexible, e.g., hard rubber, to facilitate removal of the mandrel from the undercut articles formed thereon. Thus, after the article is formed, the mandrel is removed from the undercut article because of the mandrel's flexibility without deforming the formed article.
There are disadvantages in using the rubber mandrel. The mandrel's flexiblity does not permit formation of articles having sharp, intricate design as can be produced by utilizing a solid mandrel.
Another disadvantage is in cooling the article, particularly plastic articles which are formed about the undercut mandrel. Non-uniform cooling may produce cracks due to localized stresses to be found in the molding material. Thus, water tubes are placed within the rubber mandrel in order to provide a more uniform cooling of the material surrounding the mandrel. However, due to the poor heat conduction characteristics of a rubber mandrel, a certain amount of non-uniform cooling is unavoidable.